Polyurethane foam for thermal insulation at extremely low temperatures

Abstract

A polyurethane foam for thermal insulation at extremely low temperatures. The abstract of the disclosure is submitted herewith as required by 37 C.F.R. §1.72(b). As stated in 37 C.F.R. §1.72(b): A brief abstract of the technical disclosure in the specification must commence on a separate sheet, preferably following the claims, under the heading “Abstract of the Disclosure.” The purpose of the abstract is to enable the Patent and Trademark Office and the public generally to determine quickly from a cursory inspection the nature and gist of the technical disclosure. The abstract shall not be used for interpreting the scope of the claims. Therefore, any statements made relating to the abstract are not intended to limit the claims in any manner and should not be interpreted as limiting the claims in any manner.

1 . A polyurethane foam for thermal insulation at extremely low temperatures, said polyurethane foam comprising polyisocyanate and a polyol mixture, wherein said polyol mixture comprises at least two active hydrogen atoms, a chain extender, a blowing agent, a foam stabilizer and catalysts, and wherein the proportion of urethane, ester, and aromatic rings in the polymer matrix of the polyurethane foam is between 70 and 85 wt. %, and the molecular weight per branching unit is between 500 and 700. 
     
     
         2 . The polyurethane foam as recited in  claim 1 , wherein the polyol mixture comprises the following:
 a) a polyether polyol;   b) 15 to 45 wt. % of a chain extender with the functionality 2.0;   c) 25 to 45 wt. % of an aromatic structure polyester polyol with an OH value between 200 and 280 mg KOH/g with the functionality 2.0, and   wherein the sum of the components of a), b) and c) is 100 wt. %.   
     
     
         3 . The polyurethane foam as recited in  claim 1 , wherein the chain extender consists of C4 to C6 alkanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol or 1,6-hexanediol. 
     
     
         4 . The polyurethane foam as recited in  claim 1 , wherein the chain extender consists of diethylene glycol or dipropylene glycol. 
     
     
         5 . The polyurethane foam as recited in  claim 1 , wherein the chain extender is an N-substituted diethanol amine: N-methyldiethanol amine, N-ethyldiethanol amine or N-phenyl diethanolamine. 
     
     
         6 . The polyurethane foam as recited in  claim 1 , wherein the OH value is between 500 and 750. 
     
     
         7 . The polyurethane foam as recited in  claim 1 , wherein the functionality of the basic polyisocyanate is between 2.1 and 2.9. 
     
     
         8 . The polyurethane foam as recited in  claim 1 , wherein the polurethane foam is produced by a casting or spraying method and its density is in the range of 65 to 110 kg/m 3 , preferably 70 to 90 kg/m 3 , the ratio ε77/ΔI(296-77) of the elongation at failure in the vertical foaming direction at 77 K, ε677, to the contraction in the vertical foaming direction during cooling from 296 K to 77 K, ΔI(296-77), perpendicular to the foaming direction in the range of 3.5 to 5.0 and that its compressive strength parallel to the foaming direction is in the range of 0.65 to 0.90 MPa at 296 K and 1.5 to 2.1 MPa at 77 K. 
     
     
         9 . Use of a polyurethane foam as recited in  claim 8  for the internal insulation of tanks for the storage of cryogenic fluids, in particular of liquid hydrogen (LH 2 ), wherein the polyurethane foam is deposited on the interior of the tank using the casting or spray method. 
     
     
         10 . The polyurethane foam as recited in  claim 2 , wherein the chain extender consists of C4 to C6 alkanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol or 1,6-hexanediol. 
     
     
         11 . The polyurethane foam as recited in  claim 10 , wherein:
 the OH value is between 500 and 750; and   the functionality of the basic polyisocyanate is between 2.1 and 2.9.   
     
     
         12 . The polyurethane foam as recited in  claim 11 , wherein the polurethane foam is produced by a casting or spraying method and its density is in the range of 65 to 110 kg/m 3 , preferably 70 to 90 kg/m 3 , the ratio ε77/ΔI(296-77) of the elongation at failure in the vertical foaming direction at 77 K, ε77, to the contraction in the vertical foaming direction during cooling from 296 K to 77 K, ΔI(296-77), perpendicular to the foaming direction in the range of 3.5 to 5.0 and that its compressive strength parallel to the foaming direction is in the range of 0.65 to 0.90 MPa at 296 K and 1.5 to 2.1 MPa at 77 K. 
     
     
         13 . Use of a polyurethane foam as recited in  claim 12  for the internal insulation of tanks for the storage of cryogenic fluids, in particular of liquid hydrogen (LH 2 ), wherein the polyurethane foam is deposited on the interior of the tank using the casting or spray method. 
     
     
         14 . The polyurethane foam as recited in  claim 2 , wherein the chain extender consists of diethylene glycol or dipropylene glycol. 
     
     
         15 . The polyurethane foam as recited in  claim 14 , wherein:
 the OH value is between 500 and 750; and   the functionality of the basic polyisocyanate is between 2.1 and 2.9.   
     
     
         16 . The polyurethane foam as recited in  claim 15 , wherein the polurethane foam is produced by a casting or spraying method and its density is in the range of 65 to 110 kg/m 3 , preferably 70 to 90 kg/m 3 , the ratio ε77/ΔI(296-77) of the elongation at failure in the vertical foaming direction at 77 K, ε77, to the contraction in the vertical foaming direction during cooling from 296 K to 77 K, ΔI(296-77), perpendicular to the foaming direction in the range of 3.5 to 5.0 and that its compressive strength parallel to the foaming direction is in the range of 0.65 to 0.90 MPa at 296 K and 1.5 to 2.1 MPa at 77 K. 
     
     
         17 . Use of a polyurethane foam as recited in  claim 16  for the internal insulation of tanks for the storage of cryogenic fluids, in particular of liquid hydrogen (LH 2 ), wherein the polyurethane foam is deposited on the interior of the tank using the casting or spray method. 
     
     
         18 . The polyurethane foam as recited in  claim 2 , wherein the chain extender is an N-substituted diethanol amine: N-methyldiethanol amine, N-ethyldiethanol amine or N-phenyl diethanolamine. 
     
     
         19 . The polyurethane foam as recited in  claim 18 , wherein:
 the OH value is between 500 and 750;   the functionality of the basic polyisocyanate is between 2.1 and 2.9; and   the polyurethane foam is produced by a casting or spraying method and its density is in the range of 65 to 110 kg/m 3 , preferably 70 to 90 kg/m 3 , the ratio ε77/ΔI(296-77) of the elongation at failure in the vertical foaming direction at 77 K, ε77, to the contraction in the vertical foaming direction during cooling from 296 K to 77 K, ΔI(296-77), perpendicular to the foaming direction in the range of 3.5 to 5.0 and that its compressive strength parallel to the foaming direction is in the range of 0.65 to 0.90 MPa at 296 K and 1.5 to 2.1 MPa at 77 K.   
     
     
         20 . Use of a polyurethane foam as recited in  claim 19  for the internal insulation of tanks for the storage of cryogenic fluids, in particular of liquid hydrogen (LH 2 ), wherein the polyurethane foam is deposited on the interior of the tank using the casting or spray method.